1. Field of the Disclosure
The present invention relates to lighting equipment for generating high luminance light, in particular white light, which comprises at least one radiation source, a conversion medium, and a carrier device for positioning and fixing the radiation source relative to the conversion medium. The conversion medium is arranged in the optical path of the radiation source and converts at least part of the incident light to a different spectral region, with remission thereof.
The radiation source will also be referred to as a primary light source below; the conversion medium as a secondary light source.
Further, lighting equipment according to the invention comprises a fiber feed by means of which light is guided from the primary light source via at least one light conductor which represents the fiber feed and via at least one optical element to at least one secondary light source which reflects and/or remits back at least part of the supplied light towards the optical element, the optical element causing slight shadowing of the reflected and/or remitted light. In the context of the invention, light refers to electromagnetic radiation which need not be in the visible spectral range, rather in particular IR and UV wavelengths are also within the scope of the invention.
2. Description of Related Art
White light sources can be found in numerous applications, for example in the fields of medical diagnosis or non-contact measuring methods. Other applications may comprise the lighting of buildings. Another important application field is the automotive sector, where such lighting equipment may be used in headlights or as a headlight, for example.
Up-to-date headlights in the automotive sector often comprise LED light sources, such as described in document DE 10 2008 031 256 A1, which provide for white lighting. A drawback therein is the complexity of implementing sufficient cooling and adequate removal of heat from the LED device.
Another development is aiming to connect a light source to lighting equipment via a light conductor. This allows to spatially uncouple light source and lighting equipment from each other. For generating white light, frequently a conversion medium is used which is arranged in the region of the lighting equipment. The conversion medium, also referred to as a converter, thereby enables conversion of the incident radiation in terms of wavelengths, so that white light can be generated in this manner.
U.S. Pat. No. 7,356,054 B2 describes such lighting equipment. Here, the conversion medium is directly connected to the end of the light conductor to achieve high luminance. Excitation of the conversion medium is therefore accomplished in transmission, i.e. the radiation is incident on one side of the conversion medium and is emitted via another side. Comparatively high power dissipation in the conversion medium, which may lead to heating and high thermal stress in the conversion medium may prove to be disadvantageous because heat removal is difficult with such an arrangement of radiation device and conversion medium. Both the geometry of the cooling and the limited possibility to adjust the numeral aperture NA of the excitation light through scattering are unfavorable circumstances in lighting equipment working in transmission. Also in this case light would be lost by backscattering.
According to the teachings of WO 2012 025141 this problem is solved by having a fiber diameter which is small as compared to the spacing between fiber and converter. This means that only a small special angle portion is shaded by the fiber end face. The holder of the fiber is located outside the reflector. The converter is supported within the emission region of the converted useful light. The converter additionally needs a cooling element. A holder of the converter is not shown but is necessary for implementation. This holder must have a filigree structure, so as not to shade even more light, and on the other hand must be as stable as possible to ensure high positional accuracy of the converter and reflector. Moreover, the converter needs to be positioned exactly relative to the light exit of the fiber end face. In the solution illustrated this is only possible by a complex mechanical structure.